Progressive-cavity down-hole pumps are frequently used in the petroleum industry to pump marginal wells. These pumps are typically driven by a motor mounted above the wellhead through a combination of pulleys and belts turning a drive string.
Belt-driven systems present dangers and mechanical problems, such as fast back spin, difficulty in varying the speed of the pulley system, high maintenance cost associated with belt failures, and difficulty in adjusting or replacing belts and pulleys. Ultimately, because of the frequency of belt repairs and adjustments, workers remove belt guards and do not replace them, rendering belt driven devices unsafe. Tens of thousands of dollars on a single well may be lost over time due to the operator's inability to make quick pump-speed adjustments to avoid dry pumping and for other problematic situations associated with belt drives. Common drive heads for rotary pumps also require a separate bearing section that is pressed into the housing of the main support frame for the pump. Further, prior-art pump drivers must be at least partially disassembled in order to allow pulling of the drive string from the well, a great disadvantage because any down time cuts well production.
What is needed is an integral drive head apparatus that incorporates a load-bearing section in the drive head itself, thereby eliminating the need to construct special stand-alone load bearings to support a drive string at different wells, as well as allowing pulling of the drive string without removal of the drive head from the well.